Naslov
Nonlinear waves and coherent structures generated by nanosecond laser pulses on metal surface

Autori
Lugomer, Stjepan

Izvornik
Program of seminars at the Weizmann Institute of Sciences for 2006

Vrsta, podvrsta
Ostale vrste radova, ostalo

Godina
2006

Ključne riječi
Nonlinear waves; Coherent Structures; vortex filaments; Self-organization

Sažetak
Nanosecond laser-matter interactions (LMI) cause the spontaneous formation of open-loop and closed-loop vortex filaments of various levels of the organization complexity. The closed-loop filaments appear as vortex rings, Hopf links, trefoil knots, and very complex knotted structures. By varying the laser power density we can operate in the Rayleigh-Taylor (RT) or the Richtmyer-Meskhow (RM) interaction environment. In the RM environment, a shock wave causes wave-like baroclinic vorticity deposition on the density interface which evolve into other types of coherent structres (N: J. Zabusky). That is, once the fluid acceleration in the RT/RM environment reaches a critical Reynolds number 2000 < Re < 5000 a Kelvin-Helmholtz like instability initiates roll-up of nonlinear waves into coherent co-rotating tubes (vortex filaments) of the same circulation polarity: C+C+C+... Also, RM counter-rotating filaments C+C-C+... arise with dipolar and tripolar core deformations. Further deformation and a helical instability leads to the merging of filaments, etc. We also discuss our recent paper (S. Lugomer and N.J. Zabusky) where nonlinear soliton-like structures evolve into breaking waves. References. 1. S. Lugomer and A. Maksimović, &laquo ; ; Solitons on filaments generated by ns laser pulse on metal surface, J. Appl. Phys. 82 (1997) 1374. 2. S. Lugomer &laquo ; ; Braids of vortex filaments generated by laser on metal surface&raquo ; ; Phys. Letters, A259 (1999)479. 3. Y. Fukumoto and S. Lugomer, &laquo ; ; Instability of Vortex filaments in Laser-Matter Interactions&raquo ; ; , Phys. Lett , A308 (2003)375. 4. S. Lugomer and Y. Fukumoto, &laquo ; ; Hierarchical Instability of Vortex Rings Array in Laser-Matter Interactions&raquo ; ; Fluid Dynamics Res., 36 (2005) 277. 5. N. J. Zabusky, S. Lugomer and S. Zhang, &laquo ; ; Micro-Fluid Dyanamics via Laser-surface Interactions&raquo ; ; , Fluid Dynamcs Res. 36 (2005) 291. 6. S. Lugomer and N. J. Zabusky, &laquo ; ; Nonlinear and breaking Micron Waves at the Laser-Liquefied Metal Pool&raquo ; ; Appl. Phys. Letters. 87 (2005) 204101.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

Napomena
The invited seminar was given at the "Department of Complex Physics", Weizmann Institute of Sciences, Rehovot, Israel, April 5th 2006.

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